Booster valve unit for brakes



Sept. `7, 1954 R. R. GuNpERsoN 2,688,335

BOOSTER VALVE UNIT FOR BRAKES Filed March 17, 1950 l Mrvlew "v Tu" Patented Sept. 7, 1954 Iren STATES ai.A

NT OFFICE 2,688,335 BOOSTER VALVE UNIT FOR BRAKES Ralph R. Gunderson, Chicago, Ill. Application March 17, 1950, Serial No. 150,308

Claims. l

rIhis invention relates to iluid pressure brake systems, and more particularly to an improved booster valve unit which Will permit the slack to Abe taken up in the brake system by low pressure fluid from the master cylinder, and then automatically admit iluid from a high-pressure auxiliary system under control of the master cylinder.

The unit is adapted for use on brakes of airplanes, trucks, automobiles, and the like.

'The primary object of the invention is to provide a simplified unit in which the brake nuid required to take up the slack in the system may be supplied at low pressure by 4the master cylinder, and only a small volume of fluid from the high pressure system is required to supplythe nal stopping power. This enables a small size pump to furnish the required high-pressure fluid.

The present invention is an improvement on the unit shown in my Patent No. 2,476,089, issued July 12, 1949. In the present unit, the movable parts are arranged to Abe moved back and forth in the same direction, Aand the device is easier to construct and may be accurately adjusted.

The invention is illustrated in `a preferred embodiment in the accompanying drawings, in which- Figure 1 is a longitudinal sectional view of the booster valve unit; and Fig. 2, a diagrammatic view of the brake system in which the improved unit may be used.

In the system illustrated in Fig. 2, a master cylinder unit 'l is provided with a f'oot pedal '8 for displacing brake fluid at low pressure through a conduit 9 to a booster valve unit I0, which is n the subject of the present invention. A conduit l l leads from the booster valve unit to the wheel cylinder brake l2. Brake Huid, either liquid or gas, when the brakes are released, will travel back through the master 'cylinder and conduit i3 to a reservoir I4 which may be vented to atmosphere if liquid is used. Fluid is pumped from the reservoir through a conduit l5, by means of a high-pressure pump I6 through a check valve l1 to an accumulator I8, which may be provided with a flexible diaphragm I9. The accumulator supplies high-pressure brake fluid to a conduit 20 through a port 2| in the booster valve unit IQ.

The booster valve unit l0 comprises a housing 22 provided with a low-pressure head 23 and a A high-.pressure head 24. The housing has, at the low pressure end, a cylinder 25 and an axially disposed communicating cylinder 26 of smaller diameter. Preferably, the head 23 makes a threaded connection at the end of the cylinder 2 25, as indicated at 21, and a gasket 2U insures a fluid tight fit. A port 29 is provided for connection to the conduit 9.

A compound piston 3i) has a head 3| fitting in the cylinder 25, and is shown with an O-ring 32 to make a uid tight connection. The piston has a smaller head 53 to t the cylinder 26 which is shown with an O-ring 3i, to maintain a duidtight sliding connection. The rear portion of the cylinder may be Vented to atmosphere, as shown at 35.

The compound piston 3U is hollow, and is provided at its low-pressure end with a seat 3B for a check valve 5i which is urged to closed position by means of a compression spring 38. Preferably, the check valve has an outwardly extending stem 35 to abut against an adjusting screw it which is threaded through the head 33 and held by a lock nut 4l. Thus, when the piston is in the position shown in Fig. 1, the check valve is held open. The high-pressure end of the piston has a threaded head l2 provided with fluid openings i3. The head may be removed to install the check-valve 3l and its spring 33. The cylinder 25 communicates with an enlarged chamber lli which has a side port 45 to which the conduit il may be attached.

The high-pressure head 2li is shown with a threaded connection at 46 to the main housing, and a gasket i? is provided to insure a uid tight connection. The head 24 is hollow and is shown With a valve chamber i8 provided With a seat i9 for a valve member 5@ which is urged into closed position by means of a compression spring 5|. One end of the valve member is provided with a hollow shank 52, so that when the valve member is pressed away from its seat i9 by pressure of the piston 35, high pressure uuid will be admitted by the opening 2| to the chamber lili. A compression spring 53 is shown in the chamber 44 urging the piston 30 away from the high pressure head 24. It will be understood that, if the unit is mounted vertically, the spring 53 would be omitted, and that its function might be performed by gravity or other pressure means.

The outer end of the valve member has a shank 55 slidably mounted in a cylinder 55 provided with a threaded plug 56. An 0-ring 51 is shown to maintain a fluid tight connection, and a vent 55 is provided for the cylinder 55. As the shank 5d has the same area as the opening in the valve seat 49, the piston 30 will not have to overcome the pressure of the fluid in the cham- -ber 4t in opening the valve. Preferably a checkvalve (not shown) is provided n the conduit 20 adjacent to the opening 2|, so that no liquid can escape from the high pressure end of the unit, even though the high pressure source should fail. Under those conditions, the brakes could still be applied by the master cylinder Without any aid from the high pressure head.

Operation When it is desired to apply the brakes, pressure is exerted on the pedal 8, so as to` displace fluid from the master cylinder through the conduit 9 and the piston 30 to the wheel cylinders l2. As pressure builds up in the system, the piston 30 will begin to move towards the high pressure end, because the area of the head 3| is larger than the area of the head 26. With this movement the valve 31 will be closed by the spring 38, and when the piston has traveled a short distance, depending on the adjustment of the screw 40, it will engage the shank 52 to open the valve 50 and admit high pressure brake fluid to the wheel cylinders. As the pressure increases, the piston 3G will be forced back towards the master cylinder side and the admission of high pressure fluid is controlled in a direct ratio to the low pressure force applied to the pedal 8. Thus, it will be understood that the application of the brakes is fully controlled by the pedal at all times.

When the pedal pressure is relaxed, the piston moves back to the low pressure end and the valve 3l is opened, so that the excess fluid, which Was admitted through the high pressure side, travels back through the master cylinder to the reservoir I4.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, for some modiiications will be obvious to those skilled in the art.

I claim:

1. A booster valve unit for a fluid pressure brake system, comprising: a housing providing a low-pressure head structure for a control cylinder of one diameter, adapted to be connected at one end to a master-cylinder, and an axially disposed. communicating cylinder of smaller diameter communicating with an opening adapted to be connected to wheel cylinders; a compound piston making fluid tight sliding connections with said control cylinder and said communicating smaller cylinder, said low-pressure cylinder having a vent to the side of the piston away from the low-pressure head; a check-valve in said compound piston controlling communication therethrough, said check-valve having a portion which will engage said low-pressure head and open communication through the piston when said piston is moved a predetermined distance towards said head; pressure means urging the piston toward the head to open the check-valve; and a high-pressure head including a valve having a movable member controlling communication from a source of high-pressure fluid to said opening to the wheel cylinders, and said valve member having a portion which will be engaged by the piston to open communication with the source of high-pressure uid when said .piston is moved a predetermined distance towards said high-pressure head.

2. A booster valve unit for a fluid pressure system, comprising: a' housing having a high pressure chamber with a head structure and an axially disposed low pressure chamber with a head; an opening in the low-pressure cylinder for connection to a master-cylinder; a pressure-movable member having a large head of one area in said low pressure chamber and a second head of smaller area in said high pressure chamber; a vent in the housing between the heads of the pressure-movable member; an operating opening to the high-pressure chamber, a valve seat in an opening through said pressure-movable member; a valve-member fitting said seat and having a portion which will engage the low-pressure head to open communication through the seat when the pressure-movable member moves a predetermined distance towards the head of the lowpressure chamber; pressure-means urging said movable member towards said low-pressure head; said head for said high-pressure chamber having a valve seat in an opening to a source of highpressure fluid; and another valve-member fitting said last mentioned seat to control communication from said high-pressure course to said highpressure chamber, said last mentioned valvemember having a portion which will be engaged by the pressure-movable member and open communication between the high-pressure source and the high-pressure chamber when the pressuremovable member is moved a predetermined distance away from the low-pressure head.

3. A device as specified in claim 1, in which the high-pressure head is hollow to form a chamber for the valve, the slidable valve member has a shank, opposite its seating portion, which makes a liquid tight connection With said head.

4. A device as specified in claim 1, in which the valve member is positioned to move axially with respect to the control cylinder and piston.

5. A device as specified in claim 2, in which the pressure movable-member is a compound piston with one of its two heads making a sliding fluid tight connection with the high pressure chamber and the other head with the low pressure chamber.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,476,089 Gunderson July 12, 1949 2,476,378 Majneri July 19, 1949 2,501,941 Hollerth Mai'. 28, 1950 

